The present invention relates to circuit switched domain services. More particularly, the present invention relates to providing circuit switched (CS) domain services over a packet switched (PS) network.
When introducing LTE (Long Term Evolution)—the next generation radio access in 3GPP—there are only packet bearers available. This means that the wide range of services currently offered within the CS domain can not be used by a terminal using LTE-connectivity, unless the terminal either shifts to another radio access or is equipped with a second transceiver permitting parallel access to the CS-domain present in 2G and 3G networks. Examples of existing services are:                Prepaid        Regularity equipments for identity signaling        Legal interception        0800 calls, free calls        Announcements        Premium number calls        Home Zone        Sound Logo        Call Barrings        MultiSIM        Standardized supplementary services        
The basic assumption when introducing LTE is that the telecommunication service will be provided by the IMS (IP Multimedia Subsystem) system.